Indicating timing advance groups

Abstract

The embodiment of the invention relates to equipment, a method and a device for indicating a timing advance group (TAG) and a computer readable storage medium. The method includes: during a random access procedure, receiving, at a terminal device from a network device, a flag mappable to a timing advance group identifier (TAG ID) associated with a serving cell of the terminal device, where the terminal device is configured with two TAGs associated with the serving cell, and the TAG ID is associated with one of the two TAGs; and determining the TAG ID based at least on a mapping between the flag index value and the TAG ID index value.

Description

[0001] TECHNICAL FIELD Embodiments of the present disclosure generally relate to the field of telecommunications, and more specifically to devices, methods, apparatuses, and computer-readable storage media indicating timing advance groups (TAGs). BACKGROUND

[0002] Main targets of multiple input multiple output (MIMO) enhancements can involve beam management, multi-transmit and receive point (mTRP) for ultra-reliable low latency communications (URLLC), mTRP for enhanced mobile broadband (eMBB), and time division duplexing (TDD) / frequency division duplexing (FDD) reciprocity. SUMMARY

[0003] In a first aspect, an apparatus is provided. The apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, during a random access procedure, a flag that is mappable to a timing advance group identification (TAG ID) associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and determine the TAG ID based at least on a mapping between an index value of the flag and an index value of the TAG ID.

[0004] In a second aspect, an apparatus is provided. The apparatus includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: transmit, during a random access procedure, to a terminal device, a flag that is mappable to a TAG ID associated with a serving cell of the apparatus, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

[0005] In a third aspect, a method is provided. The method includes: receiving, during a random access procedure, at a terminal device from a network device, a flag that is mappable to a timing advance group identification (TAG ID) associated with a serving cell of the terminal device, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and determining the TAG ID based at least on a mapping between an index value of the flag and an index value of the TAG ID.

[0006] In a fourth aspect, a method is provided. The method includes: transmitting, during a random access procedure, from a network device to a terminal device, a flag that is mappable to a timing advance group identification (TAG ID) associated with a serving cell of the network device, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

[0007] In a fifth aspect, there is provided an apparatus comprising: means for receiving, during a random access procedure, a flag that is mappable to a timing advance group identity, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and means for determining the TAG ID based at least on a mapping between the flag index value and the TAG ID index value.

[0008] In a sixth aspect, there is provided an apparatus comprising: means for transmitting, during a random access procedure, to a terminal device, a flag that is mappable to a timing advance group identity, TAG ID, associated with a serving cell of the apparatus, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

[0009] In a seventh aspect, there is provided a computer readable medium having stored thereon a computer program, which, when executed by at least one processor of an apparatus, causes the apparatus to perform the method according to the third or fourth aspect.

[0010] Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments, to be read in conjunction with the accompanying drawings, which illustrate the principles of the embodiments of the present disclosure by way of example. BRIEF DESCRIPTION OF DRAWINGS

[0011] Embodiments of the present disclosure are presented in the context of examples, and their advantages are explained in more detail below with reference to the drawings.

[0012] Figure 1 An example environment in which example embodiments of the present disclosure can be implemented is shown; Figure 2 Signaling diagrams illustrating examples of procedures according to some example embodiments of the present disclosure are shown; Figure 3 Examples of message formats according to some example embodiments of the present disclosure, in which a flag indicating a TAG can be included, are shown; Figure 4 Flowcharts illustrating example methods of indicating a TAG according to some example embodiments of the present disclosure are shown; Figure 5 Flowcharts illustrating example methods of indicating a TAG according to some example embodiments of the present disclosure are shown; Figure 6 Simplified block diagrams of devices suitable for implementing example embodiments of the present disclosure are shown; and Figure 7 Block diagrams of example computer readable media according to some embodiments of the present disclosure are shown.

[0013] In all of the drawings, like or similar reference numerals can refer to like or similar elements throughout the several views. DETAILED DESCRIPTION

[0014] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described for illustrative purposes only and are helpful in understanding and practicing the present disclosure, but do not imply any limitation on the scope of the present disclosure. The embodiments described herein can be implemented in various ways other than those described below.

[0015] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein can have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0016] Reference throughout this disclosure to “one embodiment”, “an embodiment”, “example embodiment” or similar terms means that a described embodiment can include a particular feature, structure, or characteristic, but every embodiment can not necessarily include the particular feature, structure, or characteristic. Moreover, these terms do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that

[0017] It should be understood that although the terms “first”, “second”, etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed terms.

[0018] As used herein, “at least one of ” and “one or more of ” and similar phrases, where the list of two or more elements is bound by “and” or “or”, means at least one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0019] As used herein, unless expressly stated otherwise, performing a step “in response to A” does not indicate that the step is performed immediately following the occurrence of “A”, and can include one or more intervening steps.

[0020] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes," "including," "has," "have," "having," "contains" and / or "containing," when used herein, specify the presence of stated features, elements and / or components and do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0021] As used in this application, the term "circuitry" can refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in pure analog and / or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processors) that (c) hardware circuit(s) that requires software (e.g., firmware) for operation, but software is not considered as hardware in and of itself, such as a processor and memory that require software to operate.

[0022] This definition of circuitry applies to all uses of this term in this application. As a further example, as used herein, the term "circuitry" also covers an implementation that has a processor and memory (or equivalents such as static storage memory or equivalents) that can store data and program instructions that, in combination with the processor, cause the device to carry out various functions described herein. For example, as used herein, the term "circuitry" also covers an implementation that has multiple processors and multiple memories (or equivalents such as static storage memory or equivalents), which can store data and program instructions that, in combination with the multiple processors, cause the device to carry out various functions described herein. As a further example, as used herein, the term "circuitry" also covers an implementation that has a processor and associated storage medium (such as a processor with a memory that stores program instructions for the processor), which can store data and program instructions that, in combination with the processor, cause the device to carry out various functions described herein. As a further example, as used herein, the term "circuitry" also covers an implementation that has multiple processors and associated storage medium (such as multiple processors that share a common memory), which can store data and program instructions that, in combination with the multiple processors, cause the device to carry out various functions described herein. As a further example, as used herein, the term "circuitry" also covers an implementation that has a processor and memory that require software or firmware for operation, even if the software or firmware is not physically present.

[0023] As used herein, the term “communication network” refers to a network following any suitable communication standard, such as New Radio (NR), Long Term Evolution (LTE), Long Term Evolution-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT), Enhanced Machine Type Communications (eMTC), etc. In addition, communication between terminal devices and network devices in a communication network can be performed according to any suitable generation communication protocol, including but not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G), sixth generation (6G) communication protocols, and / or any other protocols that are currently known or developed. Embodiments of the present disclosure can be applied in various communication systems. In light of the rapid development of communication, it is inevitable that future types of communication technology and systems that can implement the present disclosure will emerge. The scope of the present disclosure should not be seen as being limited to the above-described systems.

[0024] As used herein, the terms “network device,” “radio network device,” and / or “radio access network device” refer to a node in a communication network via which terminal devices access the network and receive services therefrom. The network device can refer to a base station (BS) or an access point (AP), e.g., a Node B (NodeB or NB), an evolved Node B (eNode B or eNB), an NR NB (also known as gNB), a remote radio unit (RRU), a remote radio head (RRH), a relay, an integrated access and backhaul (IAB) node, a low power node (such as a femto, pico, non-terrestrial network (NTN)), or a non-terrestrial network device (such as a satellite network device, low earth orbit (LEO) satellite, and geosynchronous earth orbit (GEO) satellite), an aerial vehicle network device, etc., depending on the terminology used and technology applied. In some example embodiments, a low earth orbit (RAN) split architecture includes a centralized unit (CU) and a distributed unit (DU). In some other example embodiments, part of or the entirety of a radio access network device can be contained on an on-board or space-borne NTN vehicle.

[0025] The term “terminal device” refers to any end device with wireless communication capability. By way of example and not limitation, a terminal device can refer to a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). A terminal device can include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over Internet Protocol (VoIP) phone, a wireless local loop phone, a tablet, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device such as a digital camera, a game terminal device, a music storage and playback appliance, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded equipment (LEE), a laptop mounted equipment (LME), a USB dongle, a smart device, a wireless customer-premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head-mounted display (HMD), a vehicle, a drone, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in an industrial and / or an automated processing chain context), consumer electronics, devices operating on a business and / or industrial wireless network, etc. A terminal device can also correspond to a mobile terminal (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device,” “communication device,” “terminal,” “user equipment,” and “UE” can be used interchangeably.

[0026] As used herein, the terms “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” can refer to any resource used to perform communication, such as a resource in a time domain, a resource in a frequency domain, a resource in a spatial domain, a resource in a code domain, or any other resource that enables communication, etc. Hereinafter, unless explicitly stated, resources in both the frequency domain and the time domain will be used as examples of transmission resources to describe some example embodiments of the present disclosure. Note that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0027] As used herein, the term “transmission reception point (TRP)” can refer to an antenna port or an antenna array (with one or more antenna elements) available at a network device located at a particular geographic location. For example, a network device can be coupled with multiple TRPs in different geographic locations to achieve better coverage. Alternatively or additionally, multiple TRPs can be incorporated into a network device, or in other words, a network device can include multiple TRPs. The term “TRP” can also be referred to as a cell, such as a macro cell, a small cell, a pico cell, a femto cell, a remote radio head, a relay node, etc. It should be understood that the term “TRP” can refer to a logical concept that can be physically implemented in various ways. For example, a TRP can refer to or correspond to a physical cell identity (PCI) or a control resource set (CORESET) pool index (i.e., CORESETPoolIndex). In example embodiments of the present disclosure, the term “TRP” can be used interchangeably with the term “PCI” or “CORESETPoolIndex”.

[0028] Figure 1 An example communication network 100 in which embodiments of the present disclosure can be implemented is shown. As shown, the communication network 100 can include a terminal device 110. Hereinafter, the terminal device 110 can also be referred to as a UE. Figure 1

[0029] The communication network 100 can also include a network device 120 that provides a serving cell 102 for the terminal device. The terminal device 110 can communicate with the network device 120 within the coverage of the serving cell 102.

[0030] In certain scenarios, the serving cell can be configured with multi-TRP (MTRP), e.g., a first TRP and a second TRP. When the terminal device 110 communicates with the network device 120 within the serving cell 102, the terminal device 110 can communicate with one or both of the first TRP and the second TRP. For example, the terminal device can be allowed to transmit and / or receive control information and data from the first TRP and the second TRP.

[0031] It should be understood that the number of network devices and terminal devices shown in FIG. 1 is for illustration only and does not imply any limitation. The communication network 100 can include any suitable number of network devices and terminal devices. Figure 1

[0032] ​​In some example embodiments, a link from a network device 120 to a terminal device 110 can be referred to as a downlink (DL), while a link from a terminal device 110 to a network device 120 can be referred to as an uplink (UL). In the DL, the network device 120 is a transmission (TX) device (or transmitter) and the terminal device 110 is a reception (RX) device (or receiver). In the UL, the terminal device 110 is a TX device (or transmitter) and the network device 120 is an RX device (or receiver).

[0033] Communications in the communication environment 100 can be implemented in accordance with any suitable communication protocol, including but not limited to, first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), fifth generation (5G), sixth generation (6G), and / or the like cellular communication protocols, wireless local area network communication protocols (such as for Institute of Electrical and Electronics Engineers (IEEE) 802.11 and / or the like), and / or any other currently known or future developed protocol. Moreover, communications can utilize any suitable wireless communication techniques, including but not limited to: code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), frequency division duplexing (FDD), time division duplexing (TDD), multiple-input multiple-output (MIMO), orthogonal frequency division multiplexing (OFDM), discrete Fourier transform spread OFDM (DFT-s-OFDM), and / or any other techniques.

[0034] As noted above, MIMO has been widely applied in current wireless communication systems. In particular, MIMO is one of the key technologies in NR systems and has been successful in commercial deployments. In 3GPP Releases 15 / 16 / 17, MIMO features were studied and specified for both frequency division duplex (FDD) and time division duplex (TDD) systems, most of which are for downlink MIMO operation.

[0035] In 3GPP Release 18, it is important to identify and specify necessary enhancements for uplink MIMO, while also introducing necessary enhancements on downlink MIMO to facilitate the use of massive antenna arrays (not only for frequency range (FR) 1, but also for FR2) to meet the requests for NR deployment evolution. This includes the following enhancement areas.

[0036] First, in commercial deployments, especially in multi-user MIMO (MU-MIMO) scenarios, significant performance loss of UEs in high / medium speed has been observed. Since this performance loss is partly caused by outdated channel state information (CSI), enhancements on CSI acquisition to mitigate such loss can be beneficial.

[0037] Second, in Rel-17, a unified transmission configuration indicator (TCI) framework was introduced that facilitates pipelined multi-beam operation for FR2. Since Rel-17 focuses on single-TRP use cases, it is beneficial to extend the unified TCI framework to focus on multi-TRP use cases.

[0038] Third, due to increasing multiplexing capacity requirements for downlink and uplink demodulation reference signals (DMRS) from various use cases, there is a need to increase the number of orthogonal ports for DMRS.

[0039] Fourth, in Rel-16 / 17, functionality was introduced to facilitate multi-TRP deployments, focusing on non-coherent joint transmission (NC-JT). Since coherent joint transmission (CJT) improves coverage and average throughput in commercial deployments with high-performance backhaul and synchronization, enhancements on CSI acquisition for FDD and TDD for FR1 can be beneficial in extending the applicability of multi-TRP deployments.

[0040] Fifth, as advanced UEs (e.g., CPE, fixed wireless access (FWA), vehicles, industrial devices) become more relevant, introducing necessary enhancements to support 8 antenna ports and uplink (UL) transmission of 4 layers and more can provide needed improvements in UL coverage and average throughput.

[0041] Sixth, as functionality for UL panel selection was introduced in Rel-17, advanced UEs (e.g., CPE, FWA, vehicles, industrial devices) can benefit in higher UL coverage and average throughput by simultaneously performing UL multi-panel transmission. Finally, some further enhancements to facilitate UL multi-TRP deployments through two TAs and enhanced UL power control can provide additional UL performance improvements.

[0042] Furthermore, in Rel-18, more enhancements for multi-TRP scenarios are expected. In one example, it is expected that CSI reporting enhancements for high / medium speed UEs will be studied, by leveraging time-domain correlation / Doppler domain information to assist DL precoding, targeting FR1, as follows: Rel-16 / 17 Type II codebook improvements (without modifying spatial and frequency domain basis); and UE reporting time-domain channel properties measured by CSI-RS for tracking.

[0043] In another example, it is expected that the Rel-17 unified TCI framework will be studied for extension to indicate multiple DL and UL TCI states, focusing on multi-TRP use cases, with the use of the Rel-17 unified TCI framework.

[0044] In further examples, it is expected that enhancements for downlink and uplink MU-MIMO with orthogonal DMRS ports (without increasing DM-RS overhead) will be studied, only for CP-OFDM. In particular, a unified design between DL and UL DMRS is sought, and up to 24 orthogonal DM-RS ports are supported, with the maximum number of orthogonal ports doubled for both single-symbol and double-symbol DMRS for each applicable DMRS type.

[0045] In further examples, it is expected that enhancements for CSI acquisition for CJT will be studied, for FR1 and up to 4 TRPs, assuming ideal backhaul and synchronization, and same number of antenna ports across TRPs, as follows: Improvements to Rel-16 / 17 Type II codebook for FDD-oriented CJT multi-TRP and its associated CSI reporting, with trade-off between throughput and overhead in mind.

[0046] SRS enhancements for managing inter-TRP cross-SRS interference for TDD-oriented CJT, by means of SRS capacity enhancement and / or interference randomization, with the following constraints: 1) no extra SRS resources are consumed; 2) multiplexing the existing SRS comb structure; 3) no new SRS root sequence.

[0047] Furthermore, the maximum number of CSI-RS ports per resource remains the same as in Rel-17, i.e., 32.

[0048] In further examples, enhancements to UL DMRS, SRS, SRI, and transmit precoding matrix indication (TPMI) (including codebooks) are expected to be studied to enable 8 Tx UL operation, supporting 4 layers and above per UE UL for CPE / FWA / vehicle / industrial devices.

[0049] In further examples, the following items are expected to be studied to facilitate simultaneous multi-panel UL transmission to achieve higher UL throughput / reliability, with focus on FR2 and multi-TRP, assuming up to 2 TRPs and up to 2 panels, targeting CPE / FWA / vehicle / industrial devices (as applicable): UL precoding indication for PUSCH, with no new codebook introduced for multi-panel simultaneous transmission. The total number of layers across all panels is up to four, and the total number of codewords across all panels is up to two, with single-DCI and multi-DCI based multi-TRP operation in mind.

[0050] UL beam indication for physical uplink control channel (PUCCH) / physical uplink shared channel (PUSCH) where unified TCI framework extension is expected, where single downlink control information (DCI) and multi-DCI based multi-TRP operation is considered. For multi-DCI based multi-TRP operation, only for the case of combination of PUSCH and PUSCH, or combination of PUCCH and PUCCH transmitted across two panels in the same component carrier (CC).

[0051] In further examples, it is expected to study and, if reasonable, specify the following: two TA for UL multi-DCI for multi-TRP operation; power control for UL single-DCI for multi-TRP operation, where unified TCI framework extension in target 2 is assumed.

[0052] In summary, operation in multi-TRP scenarios is a technical concern. In this disclosure, a solution for related transmission is proposed for the scenario where at least two TA values are configured for a UE within a serving cell. Some related technical implementation ways are listed below.

[0053] In some embodiments, enhancements on two TA for UL multi-DCI for multi-TRP operation are supported. In addition, the network can signal two TACs, or the network can signal one TAC and the UE can derive the second TA.

[0054] In some embodiments, two TA enhancements for intra- and inter-cell multi-DCI multi-TRP scenarios are supported. In addition, enhancements on two TA for UL multi-DCI for multi-TRP operation apply to both FR1 and FR2.

[0055] In some embodiments, two TA enhancements for multi-DCI based multi-TRP operation apply at least to: TDM based multi-DCI uplink transmission, while multi-DCI uplink transmission (if simultaneous uplink multi-DCI uplink transmission is supported).

[0056] In some embodiments, for multi-DCI multi-TRP operation with two TAs, the following alternatives are expected to be studied: consider two reference timings (i.e., timing of DL reception), consider one reference timing.

[0057] In some embodiments, for multi-DCI multi-TRP operation with two TAs, either of the following alternatives can be supported: one n-TimingAdvanceOffset value per serving cell, or two n-TimingAdvanceOffset values per serving cell.

[0058] In some embodiments, for multi-DCI based multi-TRP operation, one of the following two alternatives can be selected: two TAGs are configured within a serving cell, or two TAs are considered within one TAG within a serving cell.

[0059] In some embodiments, for multi-DCI based multi-TRP operation with two TAs, several solutions can be adopted for the overlapping part between two UL transmissions associated with the two TAs, including introducing scheduling restriction in the overlapping part, introducing dropping rule, and allowing overlapping transmission in case the UE supports STxMP transmission.

[0060] In some embodiments, for multi-DCI based multi-TRP operation with two TAs, two TAGs belonging to a serving cell can be configured.

[0061] In some embodiments, for multi-DCI multi-TRP operation with two TAs, up to two n-TimingAdvanceOffset values per serving cell can be supported.

[0062] In some embodiments, multi-DCI based multi-TRP operation with two TAs can be applied to the following cases: RACH triggered by physical downlink control channel (PDCCH) order in intra-cell MTRP case; RACH triggered by PDCCH order in inter-cell MTRP case; RACH triggered by contention-based RA (CBRA) or contention-free RA (CFRA) in radio resource control (RRC) connected mode by the UE.

[0063] In some embodiments, for associating a TAG with a target UL channel / signal for multi-DCI based multi-TRP operation, one of the following options can be selected: Option 1: associate a TAG with a TCI state / space relation; Option 2: associate a TAG with a CORESETPoolIndex; Option 3: associate a TAG with a DL reference signal (RS) group. For UL transmission, the UE adopts the TAG associated with the DL RS group to which the PL RS of the UL transmission belongs; Option 4: for semi-static UL channels / RSs, directly associate a TAG to the target UL channel / RS (e.g., periodic CSI PUCCH, periodic SRS, configured grant (CG) PUSCH), and further discuss how to associate a TAG with dynamic UL channels / RSs (e.g., by additionally associating a TAG with a CORESETPoolIndex, etc.).

[0064] In some embodiments, for multi-DCI multi-TRP operation with two TAs within a CC, two DL reference timings are supported, where each is associated with one TAG. Furthermore, the baseline assumption is that the Rx timing difference between the two DL reference timings is no larger than the CP length, and as an optional UE capability, the Rx timing difference between the two DL reference timings can be assumed to be larger than the CP length.

[0065] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, one of the following options is supported: PDCCH scheduling RAR is always received from the serving cell, no additional Type 1 common search space (CSS) is configured for each additional PCI; and in addition to PDCCH scheduling random access response (RAR) is received from the serving cell, receiving PDCCH scheduling RAR from the TRP corresponding to the additional PCI is also supported for RACH procedure associated with the additional PCI, additional Type 1 CSS configuration is supported for each additional PCI.

[0066] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, physical random access channel (PRACH) configuration associated with the configured additional PCI (different from the PCI of the serving cell) is supported.

[0067] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, a mechanism is supported to determine which PRACH configuration to use in the RACH procedure triggered by PDCCH order (i.e. use the RACH configuration corresponding to the serving cell PCI or the RACH configuration corresponding to the additional PCI).

[0068] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, one of the following options is supported: 1) PDCCH order transmitted by one TRP triggers RACH procedure to the same TRP, where PDCCH order transmitted by one TRP triggers RACH procedure to the other TRP is not allowed; 2) alternative 2: PDCCH order transmitted by one TRP triggers RACH procedure to the same TRP or different TRP, where PDCCH order triggering two RACH procedures for two TRPs can also be supported.

[0069] In some embodiments, for associating a TAG with a target UL channel / signal for multi-DCI based multi-TRP operation, the following refinements for the four options are as follows: Option 1: Associate TAG with TCI state / space relation. In addition, configure TAG ID as part of UL / joint TCI state or spatial relation, and use the TAG ID associated with the UL / joint TCI state or spatial relation for UL transmission.

[0070] Option 2: Associate TAG with CORESETPoolIndex. In addition, for dynamically scheduled / activated PUSCH, use the TAG associated with the CORESETPoolIndex of the CORESET carrying the scheduling / activation PDCCH for UL transmission. Specifically, for Type 1 CG, P / SP-SRS, and P / SP-PUCCH, the CORESETPoolIndex is configured by RRC.

[0071] Option 3: Associate TAG with SSB group. For transmission, UE adopts the TAG associated with the SSB group that the (PL) RS belongs to if the PL RS is SSB, and the TAG associated with the SSB group that the QCL source SSB of the PL RS belongs to if the PL RS is CSI-RS.

[0072] Option 4: TAG association is performed as follows: for dynamically scheduled / activated channels / signals, use the TAG associated with the CORESETPoolIndex of the CORESET carrying the scheduling PDCCH for UL transmission; for P / SP UL channels / signals (not scheduled or activated by DCI), the TAG ID is configured by RRC.

[0073] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, support enhancements related to indicating TAG ID via absolute TA command.

[0074] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, it cannot always be assumed that both TRPs are aware of the overlapping region between transmissions corresponding to the two TAs. In addition, even if the TRPs are not aware of the overlapping region, the network can apply scheduling restrictions.

[0075] In some embodiments, for intra-cell multi-DCI based multi-TRP operation with two TA enhancements, at least one of the following options is supported: Option 1: In RAR, indicate TAG ID as part of TA command; Option 2: Indicate TAG ID as part of PDCCH command; Option 3: SSBs are divided into two groups, one group per TRP. If the SSB associated with a RACH procedure belongs to the nth group (n = 1, 2), the TA obtained via this RACH procedure corresponds to the nth TRP; Option 4: RACH resources are divided into two groups, where for a RACH procedure, if the corresponding RACH resource belongs to the nth group (n = 1, 2), the TA obtained via this RACH procedure corresponds to the nth TRP; Option 5: Preambles are divided into two groups, where for a RACH procedure, if the corresponding preamble belongs to the nth group (n = 1, 2), the TA obtained via this RACH procedure corresponds to the nth TRP; Option 6: TAG ID is associated with CORESETPoolIndex and the TAG ID is determined based on the CORESETPoolIndex of the PDCCH order; Option 7: Each TCI state is associated with a TAG ID and the TAG ID corresponding to a RACH triggered by a PDCCH order is determined based on the TCI state used to receive this PDCCH order.

[0076] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, one additional PRACH configuration is supported per one configured additional PCI. In addition, this additional PRACH configuration is used in the RACH procedure for the corresponding configured additional PCI triggered by a PDCCH order.

[0077] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, CFRA (for both intra-cell and inter-cell) triggered by a PDCCH order is supported.

[0078] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, the case that a PDCCH order sent by one TRP triggers a RACH procedure pointing to the same TRP or a different TRP (at least for inter-cell multi-DCI) is supported.

[0079] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, there is no consensus on supporting enhancements of CBRA triggered by a PDCCH order.

[0080] In some embodiments, to associate TAGs with target UL channels / signals, for multi-DCI based multi-TRP operation, the following is supported: associate TAGs with TCI states; associate TAG IDs with UL / joint TCI states; for UL transmission, use the TAG ID associated with the UL / joint TCI state; baseline is that UE expects that the (active) UL / joint TCI state of (UL signal / channel) associated with one CORESET Pool Index corresponds to one TAG; UE can report that it supports that the (active) UL / joint TCI state of (UL signal / channel) associated with one CORESET Pool Index corresponds to two TAGs.

[0081] In some embodiments, for multi-DCI based inter-cell multi-TRP operation with two TA enhancements, one additional PRACH configuration is supported for each configured additional PCI, and the additional PRACH configuration is used for RACH procedure triggered by PDCCH order for the corresponding configured additional PCI.

[0082] In some embodiments, for multi-DCI based multi-TRP operation with two TA enhancements, for the case where UE does not support UL STxMP transmission, at least one of the following is introduced: Introduce a time gap X between two UL transmissions associated with two different TA values, where X symbols remain unused in the slot(s) corresponding to the two UL transmissions; Reduce the overlapping duration of one of the two UL transmissions; Apply a scheduling restriction so that the UE does not expect the two UL transmissions to overlap.

[0083] Basically, two CBRA procedures are supported, i.e., 4-step random access procedure (i.e., RACH) and 2-step random access procedure.

[0084] For example, during a 4-step RACH, a UE can transmit a specific preamble in message 1 (MSG1) to a gNB via a physical random access channel (PRACH) using specific resources called RACH occasions (ROs). The gNB can reply with a random access response (RAR) message, which can also be referred to as message 2 (MSG2). MSG2 can include a detected preamble ID, a time advance command, a temporary cell radio network temporary identifier (TC-RNTI), and a UL grant for transmission of MSG3 on PUSCH. The UE can then respond to MSG2 with an ID for contention resolution for radio resource control (RRC) request on a scheduled PUSCH, which can also be referred to as MSG3. The gNB can transmit a contention resolution message with a contention resolution ID for RRC setup, which can also be referred to as message 4 (MSG4).

[0085] Upon receiving MSG4, if the UE’s contention resolution ID is carried by MSG4, the UE can transmit an ACK on a physical uplink control channel (PUCCH). This completes the 4-step RACH. In addition, prior to MSG1, there is a preliminary step of transmitting (at the gNB) and receiving (at the UE) a synchronization signal block (SSB), including a DL beam sweep, which is not a formal part of the RACH procedure. As a result of this preliminary step, the UE can select an index of a preferred SSB beam and decode an associated physical broadcast channel (PBCH) for a master information block (MIB), a system information block (SIB), etc. The index is also used by the UE to identify a suitable RO for preamble transmission (i.e., MSG1) according to an SSB-to-RO mapping conveyed by SIB1. The SSB beam index selected by the UE can be used by the gNB for MSG2 transmission.

[0086] In a two-step random access procedure, MSG1 and MSG3 are combined in MSGA and transmitted without waiting for feedback (traditionally MSG2) from the gNB. Similarly, the gNB can combine MSG2 and MSG4 into message B (MSGB).

[0087] Contention resolution is specified for 4-step and 2-step RA procedures, where MSGB reception and contention resolution for 2-step RA type are specified as follows.

[0088] In some embodiments, once the MSGA preamble is transmitted, the MAC entity shall start the msgB-ResponseWindow at the PDCCH occasion, regardless of the possible occurrence of measurement gaps.

[0089] In some embodiments, once the MSGA preamble is transmitted, regardless of the possible occurrence of measurement gaps, the MAC entity shall monitor the PDCCH of the SpCell for a random access response identified by the MSGB-RNTI while msgB-ResponseWindow is running.

[0090] In some embodiments, once the MSGA preamble is transmitted, regardless of the possible occurrence of measurement gaps, if a C-RNTI MAC CE is included in the MSGA, the MAC entity shall monitor the PDCCH of the SpCell for a random access response identified by the C-RNTI while msgB-ResponseWindow is running.

[0091] In some embodiments, once the MSGA preamble is transmitted, regardless of the possible occurrence of measurement gaps, if a C-RNTI MAC CE is included in the MSGA, the MAC entity shall monitor the PDCCH of the SpCell for a random access response identified by the C-RNTI while msgB-ResponseWindow is running.

[0092] In some embodiments, once the MSGA preamble is transmitted, regardless of the possible occurrence of measurement gaps, if a C-RNTI MAC CE is included in the MSGA, the MAC entity shall monitor the PDCCH of the SpCell for a random access response identified by the C-RNTI while msgB-ResponseWindow is running.

[0093] In some embodiments, once the MSGA preamble is transmitted, regardless of the possible occurrence of measurement gaps, if a notification of reception of a PDCCH transmission of the SpCell is received from lower layers, if the C-RNTI MAC CE is included in the MSGA, and if a downlink assignment for the C-RNTI has been received on the PDCCH and the received TB is successfully decoded, the MAC entity shall: process the received timing advance command, consider the random access response reception successful, stop the msgB-ResponseWindow, and if the MAC PDU contains an absolute timing advance command MAC CE, consider the random access procedure successfully completed and complete the disassembly and demultiplexing of the MAC PDU.

[0094] In some embodiments, once the MSG3 is transmitted, if the MSG3 transmission (i.e., initial transmission or HARQ retransmission) is scheduled with Type A PUSCH repetition, the MAC entity shall: start or restart the ra-ContentionResolutionTimer in the first symbol after the end of all repetitions of the MSG3 transmission plus UE-gNB RTT if the MSG3 is transmitted on non-terrestrial networks; otherwise, start or restart the ra-ContentionResolutionTimer in the first symbol after the end of all repetitions of the MSG3 transmission.

[0095] In some embodiments, once the MSG3 is transmitted, if the MSG3 transmission (i.e., initial transmission or HARQ retransmission) is transmitted on non-terrestrial networks, the MAC entity shall: start or restart the ra-ContentionResolutionTimer in the first symbol after the end of the MSG3 transmission plus UE-gNB RTT.

[0096] In some embodiments, once the MSG3 is transmitted, if the MSG3 transmission (i.e., initial transmission or HARQ retransmission) is not scheduled with Type A PUSCH repetition and the MSG3 transmission (i.e., initial transmission or HARQ retransmission) is not transmitted on non-terrestrial networks, the MAC entity shall start or restart the ra-ContentionResolutionTimer in the first symbol after the end of the MSG3 transmission.

[0097] In some embodiments, once the MSG3 is transmitted, the MAC entity shall monitor the PDCCH while the ra-ContentionResolutionTimer is running regardless of the possible occurrence of measurement gaps.

[0098] In some embodiments, once MSG3 is transmitted, if a notification of reception of a PDCCH transmission of the SpCell is received from lower layers, and if a C-RNTI MAC CE is included in MSG3, the MAC entity shall: consider the contention resolution successful, stop the a-ContentionResolutionTimer, discard the TEMPORARY_C-RNTI, and consider the random access procedure successfully completed, if the random access procedure was initiated for SpCell beam failure recovery or for beam failure recovery of two BFD-RS sets of the SpCell and the PDCCH transmission is addressed to the C-RNTI, or if the random access procedure was initiated by a PDCCH order and the PDCCH transmission is addressed to the C-RNTI, or if the random access procedure was initiated by the MAC sublayer itself or by the RRC sublayer and the PDCCH transmission is addressed to the C-RNTI and contains an UL grant for a new transmission.

[0099] As mentioned above, it is expected to further discuss and develop the enhancement on two TAs for UL multi-DCI for multi-TRP operation in Rel-18. Since the current TAG ID space is 4, and if it is extended to e.g. 8 TAG IDs due to mTRP operation, it can still be needed to discuss how to indicate the TAG ID in random access procedure.

[0100] The scheme of the present disclosure proposes a mechanism for indicating TAG. In the scheme, in the case that the terminal device 100 is configured with two TAGs associated with the serving cell of the terminal device in the random access procedure, the network device can send a flag that can be mapped to a TAG ID associated with the serving cell to the terminal device, and the TAG ID is associated with one of the two TAGs. Then, the terminal device 110 can determine the TAG ID based on at least the mapping between the flag index value and the TAG ID index value.

[0101] In this way, the TAG ID for the serving cell can be indicated by a one-bit flag, which can indicate information about the TAG ID with lower overhead. In addition, the flag can be included in RAR / MSGB / fallbackRAR, where there is also lower overhead for DCI / UL grant.

[0102] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0103] Reference is now made to Figure 2 which shows a signaling diagram 200 for communication according to some example embodiments of the present disclosure. As Figure 2As shown, the signaling diagram 200 involves the terminal device 110 and the network device 120. For the purpose of discussion, reference is made to Figure 1 the signaling diagram 200 is described.

[0104] In a scenario related to Figure 2 , the serving cell 102 managed by the network device 120 can serve the terminal device 110. The terminal device 110 can be configured with two TAGs associated with the serving cell 102.

[0105] As Figure 2 shown, the network device 120 can transmit (202) a flag that is mappable to a TAG ID associated with the serving cell.

[0106] In some embodiments, the flag is introduced to indicate between the TAG IDs (e.g., two TAG IDs) associated with the serving cell 102 in which the PRACH preamble is transmitted (e.g., in MSG 1). That is, the flag can indicate which TAG ID the transmitted PRACH preamble corresponds to within the serving cell in which the PRACH preamble is transmitted.

[0107] For example, the flag can be a one-bit indication. That is, the flag serves as a one-bit flag. Since the current TAG ID can occupy 2 bits (4 indices / values) (which can be extended to a larger value (e.g., 8) for the reason of multi-TRP operation), a single reserved bit can not indicate the exact TAG ID. Therefore, a one-bit flag can be used to indicate whether the TAG ID of the serving cell has a certain index value.

[0108] In some embodiments, the flag indicating a first value can be mappable to the TAG ID among the TAG IDs associated with the serving cell that has the lowest index value, and the flag indicating a second value can be mappable to the TAG ID among the TAG IDs associated with the serving cell that has the lowest index value.

[0109] For example, the lowest index of the flag (i.e., ‘0’) can correspond to the TAG ID of the serving cell that has a lower index value (e.g., ‘0’, ‘1’, or ‘2’, etc.), while the highest index of the flag (i.e., ‘1’) can correspond to the TAG ID of the serving cell that has a higher index value (e.g., ‘1’, ‘2’, or ‘3’), or vice versa.

[0110] In some embodiments, the flag is indicated in the RAR or message B. Alternatively, the RAR used herein can also be referred to as a fallback RAR.

[0111] In some embodiments, the flag is indicated in reserved bits in the RAR or Message B. For example, a one-bit flag can replace reserved bits in the RAR or MSGB.

[0112] In some embodiments, the flag is included in the UL authorization field of the Media Access Control (MAC) payload for RAR. For example, the one-bit flag may be indicated by the first bit of the MAC payload for RAR, or by the first bit of the MAC payload for message B.

[0113] In some embodiments, a flag is included in the downlink control information (DCI) used for scheduling RAR or MSGB. For example, the flag is included in the DCI used for scheduling MAC Protocol Data Units (PDUs) for RAR or MAC PDUs for message B.

[0114] In this case, each RAR MAC PDU can be restricted to indicating the RAR associated with the same TRP (therefore, for each terminal device, the RAR is associated with the TAG ID corresponding to that TRP).

[0115] In some other embodiments, a flag is included in the DCI for scheduling UL authorization for successful contention resolution or successful random access procedure completion. In one example, a one-bit flag is included in the DCI for scheduling UL authorization for successful contention resolution or successful RA procedure completion (i.e., "PDCCH transmission is addressed to C-RNTI and contains UL authorization for new transmission"), or for scheduling DL allocation (e.g., in the case of beam fault recovery (BFR) or a 2-step RA with absolute timing advance command (TAC) MAC CE).

[0116] like Figure 2 As shown, terminal device 110 can determine (204) the TAG ID to be used for subsequent UL transmission based on the received flag and, for example, the association between the flag index value and the index value of the TAG ID. That is, the received flag can be mapped to the index value TAG ID based on this association.

[0117] Then, terminal device 110 can perform (204) subsequent UL transmission to network device in advance by using the timing corresponding to TAG ID.

[0118] Based on the solutions proposed in this disclosure, the possible impacts on the specifications can be listed as follows: Table 1: MAC payload used for random access response

[0119] Figure 3An example of a message format according to some example embodiments of the present disclosure is shown, in which a flag that indicates a TAG can be included in the message format.

[0120] In some embodiments, a flag that can be mapped to a TAG ID can be included in a TI field 301 of a MAC payload for a RAR. For example, a lowest index of the flag (i.e., '0') can correspond to a TAG ID of a serving cell having a lower index value (e.g., '0', '1', or '2', etc.), while a highest index of the flag (i.e., '1') can correspond to a TAG ID of a serving cell having a higher index value (e.g., '1', '2', or '3').

[0121] In some embodiments, a flag that can be mapped to a TAG ID can be included in a UL grant field of a MAC payload for a RAR.

[0122] Figure 4 A flowchart of an example method 400 of indicating a TAG according to some example embodiments of the present disclosure is shown. The method 400 can be implemented at a terminal device 110 as shown. For purposes of discussion, the method 400 will be described with reference to the terminal device 110 and the components of terminal device 110 as described above with respect to FIG. 1. Figure 1 The method 400 will be described with reference to the components of terminal device 110 as described above with respect to FIG. 1. Figure 1 The method 400 will be described with reference to the components of terminal device 110 as described above with respect to FIG. 1.

[0123] At 410, the terminal device 110 receives, during a random access procedure, a flag that can be mapped to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

[0124] At 420, the terminal device 110 determines the TAG ID based at least on a mapping between the flag index value and the TAG ID index value.

[0125] In some example embodiments, the flag is a one-bit indication.

[0126] In some example embodiments, a flag indicating a first value can be mapped to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell, and a flag indicating a second value can be mapped to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

[0127] In some example embodiments, the flag is indicated in a random access response, RAR, or a message B.

[0128] In some example embodiments, the flag is indicated by a first bit of a media access control, MAC, payload for the RAR, or a first bit of a MAC payload for the message B.

[0129] In some example embodiments, the flag is included in an uplink grant field in a random access response, RAR.

[0130] In some example embodiments, the flag is included in a downlink control information, DCI, for scheduling a medium access control, MAC, protocol data unit, PDU, the MAC PDU being a MAC PDU for a random access response, RAR, or a MAC PDU for a message B.

[0131] In some example embodiments, the flag is included in a downlink control information, DCI, for scheduling an uplink grant for a successful contention resolution or a successful random access procedure completion.

[0132] Figure 5 A flowchart illustrating an example method 500 of indicating a TAG according to some example embodiments of the present disclosure is shown. The method 500 can be implemented at a network device 120 as shown in Figure 1 For purposes of discussion, the method 500 will be described with reference to the network device 120. Figure 1 The method 500 is described.

[0133] At 510, the network device 120 transmits, to a terminal device during a random access procedure, a flag that is mappable to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

[0134] In some example embodiments, the flag is a one-bit indication.

[0135] In some example embodiments, the flag indicating the first value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell and the flag indicating the second value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

[0136] In some example embodiments, the flag is indicated in a random access response, RAR, or a message B.

[0137] In some example embodiments, the flag is indicated by a first bit of a medium access control, MAC, payload for the RAR or a first bit of a MAC payload for the message B.

[0138] In some example embodiments, the flag is included in an uplink grant field in a random access response, RAR.

[0139] In some example embodiments, the flag is included in downlink control information, DCI, for scheduling a media access control, MAC, protocol data unit, PDU, for a random access response, RAR, or for a message B.

[0140] In some example embodiments, the flag is included in downlink control information, DCI, for scheduling an uplink grant for a successful contention resolution or a successful random access procedure completion.

[0141] In some example embodiments, an apparatus (e.g., implemented at the terminal device 110) capable of performing the method 400 can include means for performing the respective steps of the method 400. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or software modules.

[0142] In some example embodiments, the apparatus includes means for receiving, during a random access procedure, a flag that is mappable to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs, and means for determining the TAG ID based at least on a mapping between the flag index value and the TAG ID index value.

[0143] In some example embodiments, the flag is a one-bit indication.

[0144] In some example embodiments, the flag indicating the first value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell, and the flag indicating the second value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

[0145] In some example embodiments, the flag is indicated in a random access response, RAR, or a message B.

[0146] In some example embodiments, the flag is indicated by a first bit of a media access control, MAC, payload for the RAR, or a first bit of a MAC payload for the message B.

[0147] In some example embodiments, the flag is included in an uplink grant field in a random access response, RAR.

[0148] In some example embodiments, the flag is included in downlink control information, DCI, for scheduling a media access control, MAC, protocol data unit, PDU, for a random access response, RAR, or for a message B.

[0149] In some example embodiments, the flag is included in downlink control information, DCI, used to schedule an uplink grant for successful contention resolution or successful completion of a random access procedure.

[0150] In some example embodiments, an apparatus (e.g., implemented at a TRP 120) capable of performing the method 500 can include means for performing the respective steps of the method 500. The means can be implemented in any suitable form. For example, the means can be implemented in circuitry or software modules.

[0151] In some example embodiments, the apparatus includes means for transmitting, to the terminal device during the random access procedure, a flag that is mappable to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the terminal device is configured with two TAGs associated with the serving cell, and the TAG ID is associated with one of the two TAGs.

[0152] In some example embodiments, the flag is a one-bit indication.

[0153] In some example embodiments, the flag indicating the first value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell, and the flag indicating the second value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

[0154] In some example embodiments, the flag is indicated in a random access response, RAR, or a message B.

[0155] In some example embodiments, the flag is indicated by a first bit of a medium access control, MAC, payload for the RAR, or a first bit of a MAC payload for the message B.

[0156] In some example embodiments, the flag is included in an uplink grant field in a random access response, RAR.

[0157] In some example embodiments, the flag is included in downlink control information, DCI, used to schedule a medium access control, MAC, protocol data unit, PDU, that is a MAC PDU for a random access response, RAR, or a MAC PDU for a message B.

[0158] In some example embodiments, the flag is included in downlink control information, DCI, used to schedule an uplink grant for successful contention resolution or successful completion of a random access procedure.

[0159] Figure 6is a simplified block diagram of a device 600 suitable for implementing example embodiments of the present disclosure. The device 600 can be provided to implement a communication device, for example, the first terminal device 110 or the second terminal device 120 as shown in Figure 1 Fig. 1. As shown, the device 600 comprises one or more processors 610, one or more memories 620 coupled to the processors 610, and one or more communication modules 640 coupled to the processors 610.

[0160] The communication module 640 is for bidirectional communication. The communication module 640 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interface can represent any interface necessary to communicate with other network elements. In some example embodiments, the communication module 640 can comprise at least one antenna.

[0161] The processor 610 can be of any type suitable to the local technical network, and can include one or more of the following as non-limiting examples: a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture, as non-limiting examples. The device 600 can have multiple processors such as a dedicated integrated circuit chip that is time-slaved to a clock that is synchronized with a master processor.

[0162] The memory 620 can include one or more non-transitory memories and one or more transitory memories. Examples of non-transitory memories include, but are not limited to, read only memories (ROM) 624, electrically programmable read only memories (EPROM), flash memory, hard drives, small optical discs (CD), digital video discs (DVD), optical discs, laser discs, and other magnetic and / or optical storage. Examples of transitory memories include, but are not limited to, random access memories (RAM) 622 and other volatile memories that will not maintain their state over a power cycle.

[0163] The computer program 630 includes computer-executable instructions that are executed by the associated processor 610. The instructions of the program 630 can include instructions for performing the operations / actions of some example embodiments of the present disclosure. The program 630 can be stored in a memory, for example, the ROM 624. The processor 610 can perform any suitable actions and processes by loading the program 630 into the RAM 622.

[0164] Example embodiments of the present disclosure can be implemented with the aid of the program 630, such that the device 600 can perform any processes of the present disclosure as discussed with reference to Figures 2 to 6 Fig. 1. Example embodiments of the present disclosure can also be implemented by hardware or by a combination of software and hardware.

[0165] In some example embodiments, the program 630 can be tangibly embodied in a computer-readable medium, which can be included in the device 600 (such as in the memory 620) or other storage device accessible by the device 600. The device 600 can load the program 630 from the computer-readable medium into the RAM 622 to execute. In some example embodiments, the computer-readable medium can include any type of non-transitory storage medium, such as ROM, EPROM, flash memory, hard disk, CD-ROM, DVD, etc. The term "non-transitory" as used herein is a limitation of the medium itself (i.e., tangible, not a signal) and not a limitation of the data storage durability (e.g., RAM vs. ROM).

[0166] Figure 7 An example of a computer-readable medium 700 is shown, which can be in the form of a CD, DVD, or other optical storage disk. The computer-readable medium 700 has the program 630 stored thereon.

[0167] In general, the various embodiments of the disclosure can be implemented in hardware or special-purpose circuits, software, logic or any combination thereof. Some aspects can be implemented in hardware, while other aspects can be implemented in firmware or software which can be executed by a controller, microprocessor or other computing device. While various aspects of an embodiment of the disclosure are illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein can be implemented in, as non-limiting examples, hardware, software, firmware, special-purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0168] Some example embodiments of the disclosure also provide at least one computer program product which is tangibly stored on a computer-readable medium (such as a non-transitory computer-readable medium). The computer program product includes computer-executable instructions, such as those included in program modules, executed by devices on a target physical or virtual processor to perform any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules can be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules can be stored on a storage device, either locally or remotely.

[0169] Program code for carrying out operations of the methods of the present disclosure can be written in any combination of one or more programming languages. The program code can be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, causes the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code can be entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0170] In the context of the present disclosure, computer program code or related data can be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer readable media, and the like.

[0171] The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0172] Moreover, while operations can be described as being in a specific order, it should not be understood as requiring that particular order, or that all operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing can be advantageous. Likewise, while several specific embodiments have been set forth, it should be understood that the scope of the disclosure is not limited to the specific embodiments described, but only by the claims. Unless explicitly stated, certain features of the embodiments described can also apply to every other embodiments, in any combination. Conversely, unless explicitly stated, various features of the embodiments described in the context of single embodiments can also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0173] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as example forms of implementing the claims.

Claims

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: receive, during a random access procedure, a flag that is mappable to a timing advance group identity, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and determine the TAG ID based at least on a mapping between a flag index value and a TAG ID index value.

2. The apparatus of claim 1, wherein the flag is a one-bit indication.

3. The apparatus of any one of claims 1 or 2, wherein the flag indicating a first value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell and the flag indicating a second value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

4. The apparatus of any one of claims 1 to 3, wherein the flag is indicated in a random access response, RAR, or a message B.

5. The apparatus of claim 4, wherein the flag is indicated by a first bit of a medium access control, MAC, payload for the RAR or a first bit of a MAC payload for the message B.

6. The apparatus of any one of claims 1 to 3, wherein the flag is included in an uplink grant field in a random access response, RAR.

7. The apparatus of any one of claims 1 to 3, wherein the flag is included in a downlink control information, DCI, for scheduling a medium access control, MAC, protocol data unit, PDU, that is a MAC PDU for a random access response, RAR, or a MAC PDU for a message B.

8. The apparatus of any one of claims 1 to 3, wherein the flag is included in a downlink control information, DCI, for scheduling an uplink grant for a successful contention resolution or a successful random access procedure completion.

9. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: transmit, to a terminal device during a random access procedure, a flag that is mappable to a timing advance group identity, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

10. The apparatus of claim 9, wherein the flag is a one-bit indication.

11. The apparatus of claim 9 or 10, wherein the flag indicating a first value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell, and the flag indicating a second value is mappable to a TAG ID having a lowest index value among the TAG IDs associated with the serving cell.

12. The apparatus of any one of claims 9 to 11, wherein the flag is indicated in a random access response, RAR, or a message B.

13. The apparatus of claim 12, wherein the flag is indicated by a first bit of a medium access control, MAC, payload for the RAR, or a first bit of a MAC payload for the message B.

14. The apparatus of any one of claims 9 to 11, wherein the flag is included in an uplink grant field in a random access response, RAR.

15. The apparatus of any one of claims 9 to 11, wherein the flag is included in a downlink control information, DCI, for scheduling a medium access control, MAC, protocol data unit, PDU, the MAC PDU being a MAC PDU for a random access response, RAR, or a MAC PDU for a message B.

16. The apparatus of any one of claims 9 to 11, wherein the flag is included in a downlink control information, DCI, for scheduling an uplink grant for a successful contention resolution or a successful random access procedure completion.

17. A method comprising: receiving, at a terminal device from a network device during a random access procedure, a flag mappable to a timing advance group identification, TAG ID, associated with a serving cell of the terminal device, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and determining the TAG ID based at least on a mapping between a flag index value and a TAG ID index value.

18. A method comprising: sending, from a network device to a terminal device during a random access procedure, a flag mappable to a timing advance group identification, TAG ID, associated with a serving cell of the network device, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

19. An apparatus comprising: means for receiving, during a random access procedure, a flag mappable to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the apparatus is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs; and means for determining the TAG ID based at least on a mapping between a flag index value and a TAG ID index value.

20. An apparatus comprising: ​ ​ A means for sending a flag to a terminal device during a random access procedure that is mappable to a timing advance group identification, TAG ID, associated with a serving cell of the apparatus, wherein the terminal device is configured with two TAGs associated with the serving cell and the TAG ID is associated with one of the two TAGs.

21. A computer readable medium comprising instructions, which when executed by an apparatus, cause the apparatus to perform at least the method of claim 17 or the method of claim 18.

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